The present invention relates to a polishing pad, and a chemical mechanical polishing apparatus using the same for manufacturing semiconductor devices.
A chemical mechanical polishing process is a process of flattening a semiconductor wafer among processes for manufacturing semiconductor devices, during which a chemical reaction of a polishing liquid is supplied in slurry form and mechanical polishing with a polishing pad are carried out on the wafer at the same time. In comparison to a reflow process or an etch-back process used for planarization of the wafer in conventional methods, the chemical mechanical polishing process can lead to global planarization, and can be performed at lower temperatures.
In particular, although the chemical mechanical polishing process may first involve a flattening process, it may also be applied to other processes, such as an etching process on a conductive film for formation of a bit-line contact pad and a storage node contact pad in a self-alignment contact (SAC) process. An apparatus for the chemical mechanical polishing process includes a platen having a polishing pad provided on an upper surface thereof, a slurry supplying unit to supply slurry to the polishing pad when polishing a wafer, a polishing head to compress the wafer to the platen in order to hold the wafer with respect to the polishing pad, and a polishing pad conditioner to reproduce the surface of the polishing pad. With the chemical mechanical polishing apparatus constructed as described above, the wafer is positioned on the platen while being compressed and held by the polishing head, to which the slurry is supplied from the slurry supplying unit, and then the polishing head is rotated to rotate the wafer and the platen at the same time, thereby polishing the wafer.
Meanwhile, during the chemical mechanical polishing process, the wafer can be flattened by adjusting the removal speed of a particular portion thereof. As a result, a groove pattern with a predetermined width, depth, and shape is formed on the polishing pad attached to the platen in order to allow easy flow of the slurry. The groove pattern acts as a major factor determining flow and distribution of the slurry continuously supplied during a polishing operation, and a polishing degree of the wafer.
FIG. 1a is a view illustrating a polishing pad of a conventional chemical mechanical polishing apparatus. FIG. 1b is an enlarged cross-sectional view taken along line X-X′ of FIG. 1a. 
Referring to FIGS. 1a and 1b, a general polishing pad 100 has a circular groove pattern 110 formed over the entire upper surface of the polishing pad. In addition, in a cross-section of the polishing pad 100 taken along the line X-X′, each groove of the groove pattern 100 is formed in a vertical shape, i.e., at an angle of 0 degrees with respect to the central axis of the polishing pad.
FIG. 2 is a view illustrating a conventional chemical mechanical polishing process performed in the circular groove pattern.
Referring to FIG. 2, a groove pattern 210 formed on a polishing pad 200 functions to smoothly supply a polishing agent and a compound required for the chemical mechanical polishing process, and to efficiently remove the slurry and by-products of the process. Meanwhile, with the circular groove pattern 210, distribution of fresh slurry supplied over the polishing pad 200, and distribution of the by-products are different in respective regions of the polishing pad according to the position of a nozzle and a rotational direction. In addition, distribution 220 of the slurry is provided in the same direction as the rotational direction 230 of the polishing pad, so that the distribution of the fresh slurry and the by-products are different in respective regions of the polishing pad. As a result, the circular groove pattern lowers uniformity and the speed of polishing.
Although a spiral groove pattern can be formed on the polishing pad, distribution of slurry and by-products are also different in respective regions of the polishing pad, thereby lowering the uniformity and the speed of polishing.